The Weapon Wheel

You can open the Weapon wheel by holding the L1 button. This will slow down time around you so you can comfortably access your Weapons and consumables even while in the middle of a fight. From this menu, you can access your weapons, medical supplies, traps, explosives, and throwables. Each category can be further expanded to select the specifics like selecting what recovery item you want to use, what melee weapon you want to use, etc.

You can also craft items on the fly from the Weapon Wheel, provided that you have the necessary materials and learned the recipe for the item. The early ones you can craft are the bandages and molotov cocktails.

Once you have learned the Field Repairs skill, you can also Repair your melee Weapons (found or crafted) using scrap from the Weapon Wheel. This is a very important skill that you should get as early as possible since it prolongs the durability of more powerful melee weapons like the spiked bat.